1. Field of the Invention
The present invention relates to a latch device for an automotive door, and particularly relates to a latch device in which an automotive door cannot be locked when it is in a door-open position.
2. Description of the Related Arts
In a conventional automotive door latch device, a door can be simply and easily locked by switching the latch device of the door into a locked state by an locking operation of an inside locking button of the door even if the door is in an open position. Therefore, difficulty frequently occurs when the door is closed when the inside locking button is in a locked state and the door key is locked in the vehicle cabin.
Further, in order to reduce this problem, prior art devices have been introduced such as an automotive door latch device which requires an additional entry operation such as an opening operation of a door open handle. This latch device comprises, as shown in FIG. 11, a latch B displaceable from an unlatched position to a full-latched position by engaging with a striker A, a ratchet C for holding an engagement between the latch B and the striker A by engaging with the latch B, an open lever D connected to an open handle of a door, an open link G having an engagement surface F which engages with a ratchet pin E of the ratchet C when the open lever D rotates so as to disengage the ratchet C from the latch B, and a lock lever H connected to a key cylinder and an inside lock button of the door and switched between an unlocked position for enabling an opening operation of the open link G and a locked position for disabling the opening operation of the open link G. The ratchet pin E is displaceable between a door-closed position shown by a solid line in which the the ratchet C is engaged with the latch B and an door-open position shown by a dot line in which the ratchet C is disengaged from the latch B. The open link G has a projection J which is engageable with the ratchet pin E at the door-open position but is disengageable with the ratchet pin E at the door-closed position.
In the full-latched or door-closed state shown in FIG. 11, since the projection J is disengageable with the ratchet pin E shown by the solid line, the lock lever H can be rotated clockwise by a locking operation of the inside lock button so as to move the open link G leftward, thereby the latch device can be switched to a locked state in which the engagement surface F is disengageable with the ratchet pin E.
In the unlatched or door-open state, the ratchet pin E is displaced to the door-open position shown by the dot line, and precludes the open link G from moving leftward by engaging with the projection J, thereby the lock lever H cannot be rotated clockwise and the latch device is held in the unlocked state. A facing between the pin E and the projection J can be cancelled by the opening operation of the open handle as an entry operation. The opening operation moves the open link G downward so as to make the projection J move apart from the ratchet pin E shown by the dot line, thereby the lock lever H can be rotated clockwise even when the door is in the open position.
As mentioned above, the conventional latch device shown in FIG. 11 prevents the latch device from being erroneously switched to the locked state by requiring the entry operation. However, when the same automotive vehicle is used for a long time, the driver unconsciously performs the entry operation, so that the problem mentioned above occurs.
In addition to the prior art device of FIG. 11, the applicant or the assignee of the present invention suggests, in Japanese Patent Application Laid-Open No. 7-34742, a latch device in which an automotive door cannot be locked when it is in a door-open position. As shown in FIG. 12, this latch device is substantially constituted by the same construction as that of the conventional latch device mentioned above and further comprises a sub projection K formed at a lower end of the open link G and an immovable blocker L formed in the latch body. In this latch device, when the open link G is moved downward by the entry operation, the sub projection K becomes engageable with the blocker L before the main projection J is apart from the ratchet pin E. Accordingly, even when the entry operation is performed, the clockwise rotation of the lock lever H is precluded by an engagement between the sub projection K and the blocker L, so that the latch device cannot be switched to the locked state.
The latch device shown in FIG. 12 is structured simply but a cost for manufacturing the same is unexpectedly high. Because, in the latter device, switching the lock lever H to the locked position is precluded by utilizing two engagements such as the engagement between the main projection J and the ratchet pin E and the engagement between the sub projection K and the blocker L, so that a high accuracy is required for manufacturing the parts, particularly the open lever D and the open link G. Further, a high accuracy is required for mounting a rod used for connecting the open lever D to the open handle.
There is another prior art latch device, as shown in FIGS. 13 and 14, in which an automotive door cannot be locked when it is in a door-open position. This latch device comprises a latch B rotatably mounted to a latch shaft M and engageable with a striker A fixed to a vehicle body, a ratchet C rotatably mounted to a ratchet shaft N and engageable with the latch B, an open lever D connected to an open handle of the door, an open link G releasing the ratchet C from the latch B by engaging with the ratchet C when the open lever D is rotated, a lock lever H connected to a key cylinder and an inside lock button of the door and switched between an unlocked position for enabling an opening operation of the open link G and a locked position for disabling the opening operation of the open link G, a cam member P fixed to the latch B, and a block lever S rotatably mounted to a block shaft R.
In this latch device, when the latch B is in the unlatched position, the block lever S is pushed by the cam member P, and a front end T of the block lever S is then moved into a space formed below a tip end U of the lock lever H as shown in dot line, thereby a locking rotation of the lock lever H in a clockwise direction in FIG. 14 is precluded.
In this latch device, when the block lever S is used, a high accuracy with respect to the various kinds of parts is not required and a freedom in designing the latch device is increased. However, the latch device has some disadvantages. A first problem is that the number of the parts is increased since the cam body P is used for transmitting the rotational movement of the latch B to the block lever S. A second problem is that a longitudinal length of the latch device is increased since the block lever S is disposed on an opposite side of the ratchet C on the basis of the latch B.
A third problem is that the block lever S can easily block the lock lever H supported by a shaft X perpendicular to the latch shaft M, but cannot easily block the lock lever supported by a shaft parallel to the latch shaft M. When the lock lever is supported by the shaft X perpendicular to the latch shaft M, the lock lever may be accessed by a gripping tool inserted into a gap between a window glass and the door frame with a high possibility, so that it is desirable that the lock lever is supported by the shaft parallel to the latch shaft M. A fourth problem is that three parts, i.e. the latch B, the cam member P and the block lever S are overlapped in the axial direction of the latch shaft M, as shown in FIG. 14. Due to this overlapping, a thickness, on a straight line connecting the latch shaft M and the ratchet shaft N, of the latch device becomes thick. Since the straight line substantially coincides with a moving locus of the window glass of the door, the thickness of the latch device makes design of the window glass difficult.